1. Field of the Invention
This invention relates to armored tires having a traction plate equipped ground engaging surface. A pneumatic tire is equipped with an armored peripheral track for use on construction and earthworking equipment.
The armored peripheral track has a belt constrained between anchor plates and traction plates. The track, with the anchor plates innermost, is disposed around the periphery of a pneumatic tire on the tread section thereof such that ground engaging traction plates radiate from the assembly.
2. Description of the Prior Art
Vehicles equipped with pneumatic tires which work in construction and other harsh environments are oftentimes driven on extremely detrimental or otherwise difficult road surfaces. Numerous articulated and conventional loaders, scrapers, dump trucks and graders, etc. operate in rock quarries, mines, foundries, refuse yards and other locations where the tires of the vehicle are continually exposed to puncture producing and wear inducing elements. Additionally, traction at some sites may be so limited that conventional rubber tired vehicles are disadvantaged.
As the tires for large construction type vehicles are expensive it is economically advantageous to minimize exposure to tire damaging elements. One way that this tire wear problem may be alleviated is through the use of endless track vehicles. These vehicles have high tractive efficiency, good stability, and good floatation characteristics. Bulldozers, power shovels, and cranes are often seen with dual endless track ground engaging means.
Conversely, endless track vehicles do have certain disadvantages that make them undesirable in some material handling applications. For instance, two track vehicles have speed limitations due to the track assembly. Heat generated by the track links may be severe enough at high speeds to cause premature failure of the tracks. Also road shock and vibration dampening characteristics are poor with conventional tracked vehicles.
On the other hand a vehicle having pneumatic tire is capable of relatively high speed. The tires also provide a major portion of the shock dampening function of the vehicle suspension. Thus for construction vehicles, such as loaders and dump trucks, which operate at high speed a pneumatic tire is more advantageous.
In some instances the traction plates used either in tracked vehicles or armored tire vehicles may be designed to have a high tractive interface between the vehicle and the ground. A tracked vehicle also may have better floatation characteristics than an untracked vehicle.
In order to realize the combined benefit of the endless track and the pneumatic tire it is highly desirous to combine the armor protection of a traction plate with the high speed capability of a pneumatic tire.
Many attempts to armor tires using plates held in position on the tire by means of chains, links, cables, etc. have beed tried for special applications. Specific examples of track linked over tires are shown in U.S. Pat. No. 3,601,212 to Peterson, et al and U.S. Pat. No. 3,612,624 to Stedman. These adaptations of linked tracks and pneumatic tires provide a shock dampening advantage as well as tire armoring, however, the linked track limits the speed of the vehicle due to the high frictional heat buildup in the linking components which may cause a high rate of wear in the components.
The troublesome link track systems have been improved upon by several inventions as typified by the invention disclosed in U.S. Pat. No. 3,773,394 to Grawey. In the Grawey invention the traction plates are fastened to anchor plates which accommodate a plurality of independent circumferential belts. This belt structure is positioned on the crown of the pneumatic tire and the tire is inflated into the belt and track structure. A continuous and flat interior belt surface contacts the pneumatic tire carcass and provides frictional engagement therewith.
The belt structure of the Grawey Patent includes an elastomer spacer between the edge of each anchor plate and the circumferential belt so that the belt surface, which contacts the crown portion of the tire or the tread portion of the tire, is smooth. Therefore a continuous interior belt surface contacts the pneumatic tire carcass and provides frictional engagement therewith.
The armored tire with the non-uniform cross section or tapered belt arrangement of this invention is adapted to be mounted on a wheel for use on an earthworking or transporting vehicle. The tire comprises a conventional, preferably radial, tire body having beads, body plies, sidewalls and a tread section in the crown thereof. The tread section would have a smooth surface shaped either in a concave or a convex manner to fit the tapered belt assembly rather than an aggressive traction surface.
The belt assembly would be constructed of non-flat anchor plates, a composite tapered non-uniform cross section belt, end spacer means, middle or center spacer means and traction plates fastened to the anchor plates such that the tapered belt is contained therebetween. Interior spaces bounded by the edges of each anchor plate, the tapered belt and the tread surface of the tire are not occupied by elastomer. As the tire and separate belt assembly is inflated on an appropriate wheel the tire will "grow" such that its tread will expand into the belt assembly allowing the partial extrusion of the tire tread surface elastomer into the previously mentioned unoccupied spaces.
The extrusion of the tread surface into the spaces between the anchor plates aids in the transmittal of torque between the tire and the belt assembly and consequently allows full transmission of torque between the vehicle and the ground surface with virtually no creep between the tire and the belt assembly in normal operation.
As the anchor plates and the tire tread surface have compatible cross sectional profiles the belt assembly tends to stay centered on the tire. The non-uniform cross section of the belt allows the traction plates to have a flat inner surface while at the same time allowing the anchor plates to have a non-flat profile. The cross sectional profile of the anchor plates may be either concave or convex depending on design preference. Of course the belt and the tire tread surface will be either concave or convex relative to the anchor plate to accommodate the appropriate non-flat anchor plate configuration.